1. Technical Field
The invention relates to decorative, imitation candles and, more particularly, to an imitation candle simulating a lighted wick.
2. Description of the Problem
Numerous manufacturers have attempted to meet a demand for a flameless, candle like luminary using electrical illumination. There are many imitation candles available that use incandescent lamps or LED's as a light source. These devices address people's concern with having an open flame indoors. Most of these devices try to implement the appearance of a realistic flame using a specially shaped bulb or lens that is exposed to view. Typically, the bulb or lens sits on top of a thin cylindrical sleeve, which is shaped and colored to resemble a candle. The results are typically disappointing, especially when these devices are not illuminated. The visible, flame shaped artificial light source makes the imitation candle as a whole appear artificial. The result can look more like a caricature of a candle than a real candle. The color of incandescent light can leave something to be desired in many candles as well.
U.S. Pat. No. 6,616,308 teaches an imitation candle configured to diminish any expectation on the part of an observer of seeing an open flame. U.S. Pat. No. 6,616,308 is incorporated herein by reference. Visually, the key visual element of a real flame is a rather intense spot of light, which when viewed directly, could be bright enough in a dark environment to be a source of glare. In a dark environment, for example, when the human eye is adjusted for scotopic vision, the eye cannot tolerate the large contrasts in brightness and as a result the physical outline of the flame is often lost to the eye. In the case of artificial flame structures, often the outer surface is frosted, or the body has some pigmentation so that the flame structure is itself lit up. By spreading the light from the internal light source across a larger surface area, the intensity of light at the surface is much less than the driving source. Because of this lack of point source intensity, the brain does not interpret the flame structure as a real flame. Incandescent lamps that have clear glass flame structures reveal an intense filament, but the filaments are linear, so these only appear as point sources when viewed from some distance.
One approach to creating a realistic illusion of a flame is disclosed in U.S. patent application Ser. No. 10/844,075, filed 12 May 2004, which is incorporated herein by reference. This application discloses an LED hidden within a fixture above an imitation candle body. Light emitted by the LED is directed to illuminate the candle body and wick from above. The LED is driven by a variable current to produce flickering light. The imitation wick has a reflective tip which reflects the incident light to create a small bright spot. The bright spot at the tip of the wick is sufficiently bright that even though the light source may be flickering, the intensity remains strong enough that the eye cannot see the change in intensity of the spot. At the same time, light shines past the wick and onto the candle body where it is diffused throughout a relatively large volume. The light intensities within the candle body are much lower resulting in a dramatic, flickering effect.
For standalone imitation candles that are not housed in a permanent fixture, the approach of the '075 application is more difficult to effect since there is no convenient place to hide the LED but within the candle body itself. If the effect of a lighted wick is to be reproduced it would be advantageous to produce a similar effect with a light source internal to the imitation candle.
Imitation candles that use incandescent lamps located at the tip of the candle do not produce a bright spot with the same effect as desired, at least at close distances, because the coil used in the bulb is not a true point source. The coil instead appears as a horizontal line source. Decorative applications of fiber optics have used fiber optic rods to transmit light from a central light source to a variety of emission points. Because the lighted fiber ends are small, they create a lighting effect that looks like lighted ‘hairs’, which cannot be produced by traditional light sources.
Another use of fiber optics has been as panel indicator light pipes. These have been designed and used in many forms to transmit light. No attempt, known to the present inventors, has been made to simulate illumination of an imitation wick. These have as their design objective to transmit as much light as possible from the light source into the light pipe.